What is the problem and solution to lemonade war?

In "The Lemonade War" by Jacqueline Davies, the central problem arises when siblings Evan and Jessie decide to compete against each other in a lemonade stand business, leading to escalating tensions and misunderstandings. The conflict stems from their rivalry and Jessie's desire to prove herself, especially as she feels overshadowed by Evan. The solution comes when they both realize the importance of teamwork and communication, ultimately learning to appreciate each other's strengths and the value of their relationship over competition. This resolution emphasizes the themes of family, cooperation, and the significance of understanding one another.